Our poor understanding of the etiopathogenic mechanisms by which Alzheimer?s disease (AD) starts and propagates throughout the brain stands as a critical barrier to identifying effective treatments for the disease. Extensive literature implicates synaptic dysfunction as an early mechanism affected in AD that involves progressively larger areas of the brain over time, with destabilization of neuronal network activity. This project seeks to address this gap in our understanding by examining the ability of extracellular vesicles (EVs) derived from microglia exposed to amyloid-beta (Abeta-EVs) to dysregulate synaptic function and network activity. EVs are membrane vesicles of endosomal (exosomes) or plasma membrane (ectosomes/microvesicles) origin, which are released extracellularly by most cell types. By exposing cell-type-specific adhesion receptors, EVs can interact with specific cells and deliver complex signals, including proteins, lipids and RNA between cells. Most importantly, several lines of evidence have recently suggested a role for EVs in AD and other neurodegenerative diseases. Abeta-EVs are therefore a good candidate for mediating spreading of synaptic dysfunction with destabilization of neuronal network activity in the AD brain. This will be firmly established by addressing the following specific aims: 1) to test the hypothesis that Abeta-EVs induce alterations of synaptic function and neuronal network activity; 2) to search for a molecular mechanism that is responsible for propagation of Abeta-EV induced synaptic dysfunction across neurons and abnormal neuronal connectivity; 3) to test the hypothesis that transfer of miRNA-146a, a glia-enriched microRNA involved in synaptic function, into the neuron is necessary for impairment of synaptic function and network activity caused by Abeta-EVs. These studies will be performed by combining the expertise of Dr. Verderio, one the pioneers in the EV field, with that of Dr. Arancio on synaptic dysfunction in AD, and Dr. Origlia on recordings from entorhinal cortex slices and EEG in animal models of AD. Moreover, Dr. Verderio has just developed the new elegant approach employed in the research design following a single extracellular vesicle?cell interaction using optical tweezer in primary cultures, and Dr. Origlia is capable of recording long-term potentiation from entorhinal cortex, a technique that has been rarely used (with the last publication in the US in 2004 and none of them in the AD field). Dr. Arancio was a pioneer in the technique of patch clamp recording from pairs of monosynaptically connected neurons. On the completion of these studies we will clarify whether Abeta-EVs spread synaptic dysfunction and destabilize neuronal network activity. We will also identify the molecular mechanisms underlying such phenomena. Findings derived from these studies will contribute to the design of researches and therapies for AD and a host of other neurodegenerative disorders with staggering social, economic and personal costs to the sufferers, their families and all of society.